scholarly journals Machine Learning-Based Identification Strategy of Fuel Surrogates for the CFD Simulation of Stratified Operations in Low Temperature Combustion Modes

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4623
Author(s):  
Valerio Mariani ◽  
Leonardo Pulga ◽  
Gian Marco Bianchi ◽  
Stefania Falfari ◽  
Claudio Forte
Keyword(s):  
Vapor Pressure ◽  
Relative Error ◽  
Accurate Prediction ◽  
Dynamics Simulation ◽  
Bayesian Optimization ◽  
Compression Ignition ◽  
Combustion Modes ◽  
Reid Vapor Pressure ◽  
Definition Of ◽  
Fuel Surrogates

Many researchers in industry and academia are showing an increasing interest in the definition of fuel surrogates for Computational Fluid Dynamics simulation applications. This need is mainly driven by the necessity of the engine research community to anticipate the effects of new gasoline formulations and combustion modes (e.g., Homogeneous Charge Compression Ignition, Spark Assisted Compression Ignition) to meet future emission regulations. Since those solutions strongly rely on the tailored mixture distribution, the simulation and accurate prediction of the mixture formation will be mandatory. Focusing purely on the definition of surrogates to emulate liquid phase and liquid-vapor equilibrium of gasolines, the following target properties are considered in this work: density, Reid vapor pressure, chemical macro-composition and volatility. A set of robust algorithms has been developed for the prediction of volatility and Reid vapor pressure. A Bayesian optimization algorithm based on a customized merit function has been developed to allow for the efficient definition of surrogate formulations from a palette of 15 pure compounds. The developed methodology has been applied on different real gasolines from literature in order to identify their optima surrogates. Furthermore, the ‘unicity’ of the surrogate composition is discussed by comparing the optimum solution with the most different one available in the pool of equivalent-valuable solutions. The proposed methodology has proven the potential to formulate surrogates characterized by an overall good agreement with the target properties of the experimental gasolines (max relative error below 10%, average relative error around 3%). In particular, the shape and the end-tails of the distillation curve are well captured. Furthermore, an accurate prediction of key chemical macro-components such as ethanol and aromatics and their influence on evaporative behavior is achieved. The study of the ‘unicity’ of the surrogate composition has revealed that (i) the unicity is strongly correlated with the accuracy and that (ii) both ‘unicity’ and accuracy of the prediction are very sensitive to the high presence of aromatics.

Actual issues of valuation of businesses of the economic entity

2017 ◽  
Vol 31 (2) ◽  
pp. 156-162 ◽  
Author(s):  
O. V. Schneider
Keyword(s):  
Discount Rate ◽  
Accurate Prediction ◽  
Economic Activities ◽  
Business Valuation ◽  
Economic Entity ◽  
The World ◽  
Definition Of

The article summarizes the main approaches in the definition of business valuation the economic entity. In the process of business valuation, taking into account the risks of financial and economic activities necessary to obtain information on what stage the owner implements the business will receive income. The most difficult task is the impossibility of accurate prediction in determining the level of income and the determination of a discount rate capitalization of future incomes due to the instability of the economy, both in the country and around the world.

Mapping the combustion modes of a dual-fuel compression ignition engine

2021 ◽  
pp. 146808742110183
Author(s):  
Jonathan Martin ◽  
André Boehman
Keyword(s):  
Direct Injection ◽  
Fuel Combustion ◽  
Dual Fuel ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Combustion Modes ◽  
Si Engines ◽  
Dual Fuel Combustion ◽  
Soot Emissions ◽  
Ci Engines

Compression-ignition (CI) engines can produce higher thermal efficiency (TE) and thus lower carbon dioxide (CO2) emissions than spark-ignition (SI) engines. Unfortunately, the overall fuel economy of CI engine vehicles is limited by their emissions of nitrogen oxides (NOx) and soot, which must be mitigated with costly, resource- and energy-intensive aftertreatment. NOx and soot could also be mitigated by adding premixed gasoline to complement the conventional, non-premixed direct injection (DI) of diesel fuel in CI engines. Several such “dual-fuel” combustion modes have been introduced in recent years, but these modes are usually studied individually at discrete conditions. This paper introduces a mapping system for dual-fuel CI modes that links together several previously studied modes across a continuous two-dimensional diagram. This system includes the conventional diesel combustion (CDC) and conventional dual-fuel (CDF) modes; the well-explored advanced combustion modes of HCCI, RCCI, PCCI, and PPCI; and a previously discovered but relatively unexplored combustion mode that is herein titled “Piston-split Dual-Fuel Combustion” or PDFC. Tests show that dual-fuel CI engines can simultaneously increase TE and lower NOx and/or soot emissions at high loads through the use of Partial HCCI (PHCCI). At low loads, PHCCI is not possible, but either PDFC or RCCI can be used to further improve NOx and/or soot emissions, albeit at slightly lower TE. These results lead to a “partial dual-fuel” multi-mode strategy of PHCCI at high loads and CDC at low loads, linked together by PDFC. Drive cycle simulations show that this strategy, when tuned to balance NOx and soot reductions, can reduce engine-out CO2 emissions by about 1% while reducing NOx and soot by about 20% each with respect to CDC. This increases emissions of unburnt hydrocarbons (UHC), still in a treatable range (2.0 g/kWh) but five times as high as CDC, requiring changes in aftertreatment strategy.

TWC-SCR Aftertreatment System Evaluation for a Lean Burn Gasoline Engine Operating in HCCI, SACI, and SI Combustion Modes

2016 ◽  
Author(s):  
Jordan Easter ◽  
Stanislav V. Bohac
Keyword(s):  
Conversion Efficiency ◽  
Gasoline Engine ◽  
Fuel Efficiency ◽  
Compression Ignition ◽  
Scr Catalyst ◽  
Advanced Combustion ◽  
Nox Conversion ◽  
Combustion Modes ◽  
Scr System ◽  
Nox Conversion Efficiency

Low temperature and dilute Homogenous Charge Compression Ignition (HCCI) and Spark Assisted Compression Ignition (SACI) can improve fuel economy and reduce engine-out NOx emissions to very low values, often less than 30 ppm. However, these combustion modes are unable to achieve stringent future regulations such as SULEV 30 without the use of lean aftertreatment. Though active selective catalytic reduction (SCR) with urea injection and lean NOx traps (LNT) have been investigated as options for lean gasoline engines, a passive TWC-SCR system is investigated in this work because it avoids the urea storage and dosing hardware of a urea SCR system, and the high precious metal cost of an LNT. The TWC-SCR concept uses periodic rich operation to produce NH3 over a TWC to be stored on an SCR catalyst for subsequent NOx conversion during lean operation. In this work a laboratory study was performed with a modified 2.0 L gasoline engine that was cycled between lean HCCI and rich SACI operation, or between lean and rich SI (spark ignited) combustion, to evaluate NOx conversion and reduced fuel consumption. Different lambda values during rich operation and different times held in rich operation were investigated. Results are compared to a baseline case in which the engine is always operated at stoichiometric conditions. SCR system simulations are also presented that compare system performance for different levels of stored NH3. With the configuration used in this study, lean/rich HCCI/SACI operation showed a maximum NOx conversion efficiency of 10%, while lean/rich SI operation showed a maximum NOx conversion efficiency of 60%. However, if the low conversion efficiency of lean/rich HCCI/SACI operation could be improved through higher brick temperatures or additional SCR bricks, simulation results indicate TWC-SCR aftertreatment has the potential to provide near-zero SCR-out NOx concentration and increased system fuel efficiency. In these simulations, fuel efficiency improvement relative to stoichiometric SI were 7 to15% for lean/rich HCCI/SACI with zero tailpipe NOx and −1 to 5% for lean/rich SI with zero tailpipe NOx emissions. Although previous work indicated increased time for NH3 to start forming over the TWC during rich operation, less NH3 production over the TWC per fuel amount, and increased NH3 slip over the SCR catalyst for advanced combustion systems, if NOx conversion efficiency could be enhanced, improvements in fuel economy and low engine-out NOx from advanced combustion modes would more than make up for these disadvantages.

Reduced-Scale Reid Vapor Pressure Apparatus

1955 ◽  
Vol 27 (1) ◽  
pp. 142-144 ◽  
Author(s):  
R. L. LeTourneau ◽  
J. F. Johnson ◽  
W. H. Ellis
Keyword(s):  
Vapor Pressure ◽  
Reid Vapor Pressure ◽  
Reduced Scale

Study on reconstruction and prediction methods of pressure field on blade surfaces for oil-filling process in a hydrodynamic retarder

2016 ◽  
Vol 26 (6) ◽  
pp. 1843-1870 ◽  
Author(s):  
Hongbin Mu ◽  
Wei Wei ◽  
Alexandrina Untaroiu ◽  
Qingdong Yan
Keyword(s):  
Numerical Method ◽  
Pressure Field ◽  
Structural Features ◽  
Accurate Prediction ◽  
Dynamics Simulation ◽  
Prediction Methods ◽  
Flow Data ◽  
Transient Pressure ◽  
Filling Process ◽  
Content Type

Purpose – Traditional three-dimensional numerical methods require a long time for transient computational fluid dynamics simulation on oil-filling process of hydrodynamic braking. The purpose of this paper is to investigate reconstruction and prediction methods for the pressure field on blade surfaces to explore an accurate and rapid numerical method to solve transient internal flow in a hydrodynamic retarder. Design/methodology/approach – Dynamic braking performance for the oil-filling process was simulated and validated using experimental results. With the proper orthogonal decomposition (POD) method, the dominant modes of transient pressure distribution on blades were extracted using their spatio-temporal structural features from the knowledge of computed flow data. Pressure field on blades was reconstructed. Based on the approximate model (AM), transient pressure field on blades was predicted in combination with POD. The causes of reconstruction and prediction error were, respectively, analyzed. Findings – Results show that reconstruction with only a few dominant POD modes could represent all flow samples with high accuracy. POD method demonstrates an efficient simplification for accurate prediction of the instantaneous variation of pressure field in a hydrodynamic retarder, especially at the stage of high oil-filling rate. Originality/value – The paper presents a novel numerical method, which combines POD and AM approaches for rapid and accurate prediction of braking characteristics during the oil-filling period, based on the knowledge of computed flow data.

Modeling advanced combustion modes in compression ignition engines with tabulated kinetics

2019 ◽  
Vol 247 ◽  
pp. 537-548 ◽  
Author(s):  
T. Lucchini ◽  
A. Della Torre ◽  
G. D’Errico ◽  
A. Onorati
Keyword(s):  
Compression Ignition ◽  
Compression Ignition Engines ◽  
Advanced Combustion ◽  
Combustion Modes

scholarly journals Assessment of COSMIC radio occultation retrieval product using global radiosonde data

2012 ◽  
Vol 5 (6) ◽  
pp. 8405-8434
Author(s):  
B.-R. Wang ◽  
X.-Y. Liu ◽  
J.-K. Wang
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Relative Error ◽  
Radio Occultation ◽  
Water Vapor Pressure ◽  
Specific Humidity ◽  
Radiosonde Data ◽  
Cosmic Radio ◽  
Horizontal Distance ◽  
Matching Criteria

Abstract. The radio occultation retrieval product of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation sounding system was verified using the global radiosonde from 2007 to 2010. 4 yr of samples were used to collect quantities of data using much stricter matching criteria than previous studies to obtain more accurate results. The horizontal distance between the radiosonde station and the occultation event is within 100 km, and the time window is 1 h. The comparison was performed from 925 hPa to 10 hPa. The results indicated that the COSMIC's temperature data agreed well with the radiosonde data. The global mean temperature bias was −0.09 K, with a standard deviation (SD) of 1.72 K. The water vapor pressure of COSMIC showed a systematic bias in relation to radiosonde in higher layers. The mean specific humidity bias of 925–200 hPa is about −0.011 g kg−1, with a SD of about 0.662 g kg−1. The COSMIC quality control process could not detect some abnormal extremely small humidity data which occured frequently in subtropical zone. Despite the large relative error of water vapor pressure, the relative error of refractivity is small. This paper also provides a comparison of eight radiosonde types with COSMIC product. Because the retrieval product is affected by the background error which differed between different regions, the COSMIC retrieval product could be used as a benchmark if the precision requirement is not strict.

scholarly journals Assessment of COSMIC radio occultation retrieval product using global radiosonde data

2013 ◽  
Vol 6 (4) ◽  
pp. 1073-1083 ◽  
Author(s):  
B.-R. Wang ◽  
X.-Y. Liu ◽  
J.-K. Wang
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Relative Error ◽  
Radio Occultation ◽  
Water Vapor Pressure ◽  
Specific Humidity ◽  
Radiosonde Data ◽  
Cosmic Radio ◽  
The Mean ◽  
Matching Criteria

Abstract. The radio occultation retrieval product of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Radio Occultation sounding system was verified using the global radiosonde data from 2007 to 2010. Samples of 4 yr were used to collect quantities of data using much stricter matching criteria than previous studies to obtain more accurate results. The horizontal distance between the radiosonde station and the occultation event is within 100 km, and the time window is 1 h. The comparison was performed from 925 hPa to 10 hPa. The results indicated that the COSMIC's temperature data agreed well with the radiosonde data. The global mean temperature bias was −0.09 K, with a standard deviation (SD) of 1.72 K. According to the data filtration used in this paper, the mean specific humidity bias of 925–200 hPa is −0.012 g kg−1, with a SD of 0.666 g kg−1, and the mean relative error of water vapor pressure is about 33.3%, with a SD of 107.5%. The COSMIC quality control process failed to detect some of the abnormal extremely small humidity data which occurred frequently in subtropical zone. Despite the large relative error of water vapor pressure, the relative error of refractivity is small. This paper also provides a comparison of eight radiosonde types with COSMIC product. Because the retrieval product is affected by the background error which differed between different regions, the COSMIC retrieval product could be used as a benchmark if the precision requirement is not strict.

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